**Shear rate** is the rate at which a progressive shearing deformation is applied to some material.

## Simple shear

The shear rate for a fluid flowing between two parallel plates, one moving at a constant speed and the other one stationary (Couette flow), is defined by

- ${\dot {\gamma }}={\frac {v}{h}},$

where:

*.γ* is the shear rate, measured in reciprocal seconds;
*v* is the velocity of the moving plate, measured in meters per second;
*h* is the distance between the two parallel plates, measured in meters.

Or:

- ${\dot {\gamma }}_{ij}={\frac {\partial v_{i}}{\partial x_{j}}}+{\frac {\partial v_{j}}{\partial x_{i}}}.$

For the simple shear case, it is just a gradient of velocity in a flowing material. The SI unit of measurement for shear rate is s^{−1}, expressed as "reciprocal seconds" or "inverse secondsThe shear rate for a fluid flowing between two parallel plates, one moving at a constant speed and the other one stationary (Couette flow), is defined by

- $}where:$
*.γ* is the shear rate, measured in reciprocal seconds;
*v* is the velocity of the moving plate, measured in meters per second;
*h* is the distance between the two parallel plates, measured in meters.

Or:

- $\stackrel{}{\gamma}}_{$
Or:

- ${\dot {\gamma }}={\frac {8v}{d}},$